This invention relates to logging truck-trailer combinations. It pertains particularly to an anti-load stripping and safety attachment for preventing the separation of the truck and trailer and consequent dumping of the load under heavy travel conditions.
The conventional logging truck-trailer combination comprises truck and trailer units, each mounting a transverse log bunk. The trailer is provided with a reach or tongue of substantial length. The forward end of the reach is coupled pivotably and releasably to the rearward end of the truck frame.
Because of the character of the load, which consists of logs many feet in length, supported at one end on the forward bunk and at the other end on the rearward bunk, a particular operational problem is encountered.
If the trailer reach is coupled pivotably in a fixed relation to the truck frame, it is impossible to turn a corner with a truck-trailer combination. Because of the inflexible character and great length of the logs, turning the front wheels of the truck has no steering effect whatsoever. The forward driving momentum of the load continues to drive the truck forwardly, even though the steering wheels are turned at an angle, with the front wheels skidding sideways along the road.
To overcome this problem, it is conventional practice to equip the trailer reach with sliding compensation means which allows the trailer to move freely longitudinally in relation to the truck. The present attachment is shown with two different types of sliding compensation means. In the first, a compensator shaft, which telescopes into the reach, is utilized. The outer end of the compensator shaft is connected to the rearward end of the truck.
The second type of sliding compensation means utilizes a bushing positioned longitudinally in the trailer frame to allow the reach to fit slideably therein.
In both situations, when the truck tows the trailer in an empty condition, the sliding compensation means is fixed to form a towing connection. However, when the truck tows the trailer in a loaded condition, the sliding compensation means is unfixed. The pulling force of the truck, then, is transmitted to the trailer through the logs themselves rather than through the trailer reach and its connection to the truck frame.
This leaves the sliding compensation means freely sliding so that the relative longitudinal adjustment between the truck and trailer may be made as required to make possible steering the truck around corners.
The use of sliding compensation means in this manner is a highly successful expedient in overcoming the above described problems, however, it is attended by serious disadvantages.
One of these is the time consuming and dangerous act required to couple and uncouple the truck and trailer. Under present conditions it is required that the driver or another employee get under the vehicle, which may be loaded with logs, to remove a coupling pin or release a clamp to uncouple a compensator shaft preliminary to traveling, or to couple it preliminary to unloading. This obviously exposes the person concerned to a severe hazard.
Also, when the trailer unit is subjected to a heavy drag, as it is when the trailer wheels are mired down in soft ground, or when the combination ascends a steep grade, the weight of the logs bearing on the bunks which supports them is insufficient to maintain the connection between truck and trailer. As a consequence, the ends of the logs slip off of one of the bunks and are dumped on the roadway. This is particularly true when short logs, which overhang the bunk by a few inches, are being carried. The labor required to clear the road, recouple the trailer to the truck, and reload the logs is self evident.
Anti-load stripping attachments heretofore have been known to prevent these problems. One such attachment is disclosed in my prior patent, U.S. Pat. No. 3,881,748. These prior attachments, however, have provided braking means separate from the sliding compensation means rather than braking means which act directly on the sliding compensation means. Therefore, the prior art attachments have not provided a positive brake and are not adaptable to all types of sliding compensation means.
It accordingly is the general purpose of the present invention to provide an improved anti-load stripping and safety attachment which prevents separation of the trailer from the truck in a logging truck-trailer combination under conditions of heavy load drag, as well as when coupling and uncoupling the compensation means, as above described.
It is a further object of the present invention to provide such an attachment having positive brake means.
It is a further object of the present invention to provide such an attachment that can be adapted for several forms of sliding compensation devices.